2022 Fiscal Year Annual Research Report

Development of a method to form hollow silicon spheres, with application to photovoltaic cells: experiment and computation.

Research Project

Project/Area Number	20K04293
Research Institution	Ritsumeikan University
Principal Investigator	WELLS John・C 立命館大学, 理工学部, 教授 (60301644)
Co-Investigator(Kenkyū-buntansha)	河野悠立命館大学, 理工学部, 助教 (40822838)
Project Period (FY)	2020-04-01 – 2023-03-31
Keywords	Silicon. / Hollow spheres. / Hollow jet method. / Solidification
Outline of Annual Research Achievements	Hollow silicon millispheres have been fabricated using a hollow coaxial jet for the first time. Silicon was melted in a graphite crucible at 1823 K, then ejected from the annulus of a coaxial nozzle as argon gas was injected from an inner nozzle whose inner and outer diameters are 0.4 mm and 1 mm respectively. Sphere diameters were 1 - 2 mm with spherical outer surfaces, and the frequency of formation was approximately 145 Hz. The wall thicknesses varied gradually between antipodes. The interior surfaces were somewhat non-spherical, with horn-like structures where the wall was thicker, most likely owing to silicon expansion as solidification finishes. This is the first report of such a “horn expansion structure” observed on a concave substrate.